Q&A - PSLE Math

[Nebbermind]

kamom:

Given that one and only one of the following statements is correct, which one is correct?


1)All the statements below are correct
2)None of the statements below is correct
3)One of the statements above is correct
4)All of the statements above is correct
5)None of the statements above is correct

Ans is (5), can someone explain to me :idea:

THANKS A MIL

The fact that ONLY one is correct rules out (1) and (4).

If (3) is TRUE, then (2) has to be TRUE since (1) is already FALSE. But that cannot be possible since (2) says that (3) is FALSE. Since either (3) or (2) being TRUE will contradict each other, we are left with (5).

[genevieve08]

Sorry my first answer is wrong.


But Kelly = $2900 and Susan = $1200 is not right either, working backwards:

First scenario Kelly spent $100 per day and left $500

Taking $2900 - $500 = $2400
2400 / 100 = 24 days

Taking scenario 2 for Kelly

2900 - 2300 = 600
600 / 50 = 12 days

[Winx5015]

Hi Nebbermind, tianzhu, MathIzzzFun & genevieve08,


Thanks all for your help!

Have a nice day

[Winx5015]

Hello,


Following are 2 questions on ratio.

(1). The ratio of Gopal's mass to Siew Leng's mass is 6:5. If Gopal loses 4Kg and Siew Leng gains 3Kg, Siew Leng will be 1Kg heavier than Gopal.
(a). Express siew Leng's mass as a fraction of the total mass.
(b). What is Gopal's actual mass?

(2). Seng Chye and Rani have different amounts of money. If Rani gives $24 to Seng Chye, the ratio of the amount of money she has to what Seng Chye has will be 4:9. If Seng Chye gives $21 to Rani, they will have the same amount of money.
(a). How much more money does Seng Chye have than Rani?
(b). How much money does Rani have?


Thanks!

[MathIzzzFun]

genevieve08:

Sorry my first answer is wrong.


But Kelly = $2900 and Susan = $1200 is not right either, working backwards:

First scenario Kelly spent $100 per day and left $500

Taking $2900 - $500 = $2400
2400 / 100 = 24 days

Taking scenario 2 for Kelly

2900 - 2300 = 600
600 / 50 = 12 days

Hi

in scenario 1,
Kelly spent $100 per day, Susan spent $50 per day, Kelly had $500 left.

Amount spent by Kelly = $2900 - $ 500 = $ 2400
Number of days for Kelly to spend $ 2400= $ 2400 / $ 100 = 24 days
Amount spent by Susan = 24 days x $ 50 = $ 1200 --> so Susan spent all her money and Kelly still has $500 left.

In scenario 2,
Kelly spent $50 per day and Susan spent $100 per day, Kelly had $ 2300 left.
Amount spent by Kelly = $2900 - $ $ 2300 = $ 600
Number of days for Kelly to spend $ 600 = $ 600/ $ 50 = 12
Amount spent by Kelly = $ 100 x 12 = $ 1200 --> Susan spent all her money and Kelly still have $ 600 left.

cheers.

[MathIzzzFun]

Winx5015:

Hello,


Following are 2 questions on ratio.

(1). The ratio of Gopal's mass to Siew Leng's mass is 6:5. If Gopal loses 4Kg and Siew Leng gains 3Kg, Siew Leng will be 1Kg heavier than Gopal.
(a). Express siew Leng's mass as a fraction of the total mass.
(b). What is Gopal's actual mass?

(2). Seng Chye and Rani have different amounts of money. If Rani gives $24 to Seng Chye, the ratio of the amount of money she has to what Seng Chye has will be 4:9. If Seng Chye gives $21 to Rani, they will have the same amount of money.
(a). How much more money does Seng Chye have than Rani?
(b). How much money does Rani have?


Thanks!

Hi

Q1.
a) 5/(5+6) = 5/11
b)
Gopal's mass --> 6u, Gopal's mass if he loses 4 kg --> 6u -4
Siew Leng's mass --> 5u, Siew Leng's mass if she gains 3 kg --> 5u + 3
5u + 3 = 6u - 4 + 1
1u = 6
Gopal's mass --> 6u = 36 kg

Q2.

If SC gives R $21, they will have same amount of money, so SC has $42 more than R

R's money --> 1 unit
SC --> 1 unit + $ 42

If R gives SC $24,
R's money : SC's money
-> 1 unit - $ 24 : 1 unit + $42 + $ 24
= 4 : 9

1 unit - $ 24 : 1 unit + 66
= 4 : 9

cross-multiply or equalize:

9 units - $ 216 = 4 units + $264
5 units = $ 480
1 unit = $ 96

SC's money --> 1 unit + $ 42 = $ 138
Rani's money --> 1 unit = $ 96

cheers.

[Winx5015]

Hi MathIzzzFun,


Thanks for solving my questions.

Regards

[anneshirleygilbert]

Can somebody please help with this question?


Four files cost as much as 3 storybooks. Five files cost $7.50 more than 2 storybooks. Mary spent $30 on an equal number of files and storybooks. How many files did she buy?

We tried to find cost of 1 book and cost of 1 file, and got terribly muddled. There must be an easier way. Can somebody help?

[MathIzzzFun]

anneshirleygilbert:

Can somebody please help with this question?


Four files cost as much as 3 storybooks. Five files cost $7.50 more than 2 storybooks. Mary spent $30 on an equal number of files and storybooks. How many files did she buy?

We tried to find cost of 1 book and cost of 1 file, and got terribly muddled. There must be an easier way. Can somebody help?

Hi

1 file --> 3 units
1 story book --> 4 units
1 file + 1 story book --> 7 units

5 files --> 15 units
2 storybooks --> 8 units
7 units = $ 7.50

So, 1 file + 1 story book = $ 7.50
$ 30 / $ 7.50 = 4

Mary bought 4 files and 4 story books

cheers.

[anneshirleygilbert]

Thanks a bunch, MathIzzzFun. You do make it seem so simple.